Technical Abstract:
Nitrous oxide (N2O) gas is produced by micro-organisms during nitrification and/or denitrification of fertilizer nitrogen in soil. Atmospheric emissions of N2O can be important from an agronomic standpoint since any escape of N from the soil represents N that cannot be utilized by the crop. Once in the atmosphere, N2O acts as a greenhouse gas which is 300 times more potent than carbon dioxide. The complexity of the processes controlling N2O emissions make it difficult to predict how a particular management practice or set of conditions will affect N2O emissions. This paper summarizes results of ongoing research projects throughout Minnesota which are attempting to quantify the impacts of specific management practices on N2O emissions. A study conducted in Rosemount in corn planted in a silt loam showed that N2O emissions can represent a substantial component of the total greenhouse gas budget of the cropping system. Interactions between fertilizer and tillage practices were important in controlling N2O emissions. A study in Becker in potato planted in a loamy sand showed that soils fertilized with controlled release N fertilized products lower total growing season emissions compared to the conventional urea treatment. A study conducted near Tracy showed that N2O emissions from soils under conventional drainage tended to emit less N2O than undrained soils, although the effects were not consistent across the entire field. It is clear from the studies summarized here that N2O emissions are controlled by a variety of management factors, including tillage, fertilizer, and drainage practices, as well as environmental factors including soil properties and climate. More field studies are required to identify practices that effectively reduce N2O emissions while maintaining crop production.